(UroToday.com) The 2025 GU ASCO annual meeting featured a prostate cancer session and a presentation by Dr. Alejandro Sanchez discussing SOAR, a phase II trial of image-guided oligometastatectomy and radiation therapy in recurrent prostate cancer. In a subset of patients with molecular-imaging defined recurrent oligometastatic prostate cancer, salvage oligometastatectomy with surgery and/or radiation may provide improved ADT-free survival.
SOAR is a phase II trial with oligorecurrent prostate cancer after primary prostatectomy or radiation therapy detected on Axumin (n = 11) or PSMA (n = 9) PET. Oligometastatic disease was defined as ≤ 10 total sites, either of bone only (Group A), nodal only (Group B), or bone and nodal (Group C). The overall treatment schema is as follows:
Groups A and C received adjuvant IMRT without ADT if PSA response was ≥ 1/3 decrease but remained ≥ 0.2 ng/dL:
Surgical intervention for patients with prostate cancer disease included extended pelvic and/or retroperitoneal lymph node dissection, depending on the location of the lymph nodes. The primary endpoint was a reduction in PSA by ≥ 50% at 6 months. Secondary objectives included PSA progression free-survival, ADT-free survival, and perioperative safety.
This trial accrued a total of 20 patients between September 2019 to May 2023. Two of 20 patients were enrolled in Arm A, 18 of 20 patients in Arm B, and no patients were enrolled in Arm C; within group B, 2 patients completed adjuvant radiotherapy. The median age was 65 years (IQR 61-71), 95% had an ECOG of 0, 10% were Hispanic, the median time from prostate cancer treatment to trial treatment was 2.2 (IQR 0.7-4.5) years, and median PSA was 1.3 ng/mL (IQR 0.6-3.4). All patients had a prior prostatectomy, with a median PSA of 8.1 ng/mL (IQR 5.8-11.6), with 25% having GG1-2, 50% GG3, 25% GG4, and 25% having pTanyN1. Overall, 85% of patients had a prior lymph node dissection, 35% had positive margins, and 45% had adjuvant/salvage radiotherapy + ADT. The mean number of PET identified lymph nodes (Group B) was 1.8 (range: 1-6), and the number of lymph nodes identified on pathology was a mean 5.1 (range: 1-31). The primary endpoint of reduction in PSA by ≥ 50% at 6 months was 40% (95% CI 19-64%). The secondary endpoint of PSA progression free-survival at 12 months was 74.1% (95% CI 54.8-100%), and ADT-free survival at 12-months was 71.4% (95% CI 52.7% - 96.6%):
There were no Clavien Grade III-IV complications.
Dr. Sanchez concluded his presentation discussing SOAR, a phase II trial of image-guided oligometastatectomy and radiation therapy in recurrent prostate cancer with the following take-home points:
- Treatment of oligometastatic disease after prostatectomy, identified on PET imaging, is safe, and at 12 months, ~70% of patients are free of PSA recurrence and off ADT
- Ongoing analyses include comparing imaging and pathology correlations, and comparing complete/partial responders and treatment failure
- Further research is needed to identify ideal candidates for salvage treatment
Presented by: Alejandro Sanchez, MD, Huntsman Cancer Institute at the University of Utah, Salt Lake City, UT
Written by: Zachary Klaassen, MD, MSc – Urologic Oncologist, Associate Professor of Urology, Georgia Cancer Center, Wellstar MCG Health, @zklaassen_md on Twitter during the 2025 Genitourinary (GU) American Society of Clinical Oncology (ASCO) Annual Meeting, San Francisco, CA, Thurs, Feb 13 – Sat, Feb 15, 2025.